Lumens

[Anonymous No.131170]

If you have two 1,000 lumens lights, does that equal 2,000 lumens if you set them side by side to shine on something or is it just two sets of 1,000 no matter what?

Like this flashlight. It is rated at 1,000 lumens and has 5 CREE Q5 LEDs. Am I to assume those are 200 lumens LEDs and their total is 1,000 lumens or is each one 1,000 lumens?

[Anonymous No.131171]

1000 no matter what unless you hard wire it differently

[Anonymous No.131175]

>>131171
Okay, so you are saying that two 1,000 lumen LEDs together are still only 1,000 lumens unless you hard wire them differently? How would you hardwire them to be 2,000 lumens?

[Anonymous No.131195]

>>131171

Waaa....
The comprehension in /diy/ is so fucking low.

[Anonymous No.131197]

>>131170
>>131175

That light would be comprised of five 200 lumen LEDs. If you placed two 1000 lights side by side, yes you would have 2000 lumen of light being produced.

But think of it a different way. If you have a light fixture with a 60W bulb it lights a room so bright. Now if you add another 60W bulb to that fixture (so it now has 2) it makes the room brighter, maybe not twice as bright. Same thing with the flashlights, lumen is just an X measure of light output. If you spread that light out like a flood then it seems dimmer. Put those lumens in a tight spot and it seems really bright.

Hope this helps.

[Anonymous No.131198]

>>131197
Yes, I thought it was that way, buy needed confirmation. Thanks.

[Anonymous No.131227]

>>131175
take an intro to physics class
this is diy, not teach me highschool basic physics

[Anonymous No.131243]

>>131227
Then why do they call the OP's flashlight 1,000 lumens when it technically isn't unless it uses a single 1,000 lumen LED?

Because ads and sales can't into physics.

[Pinzfag, /k/'s resident flashaholic No.131358]

First single core led flashlight to break 1000 Lumens reporting in, two hours of runtime, 600 yards of throw, variable brightness with current regulating circuitry to extend runtime.

[Anonymous No.131368]

Lumens are a measure of total light output. If you take five 200-lumen sources, plus five more 200-lumen sources (your two 1000-lumen lights), the total output is 2000 lumens.

In theory.

In reality that thing is made by a dubious Chinese manufacturer like Ultrafire and is probably not putting out 200 lumens per LED in the first place.

If you actually want to light something up and make it visible, the measure you're interested in is lux. Lux is a measure of effective illumination over an area.

[Pinzfag, /k/'s resident flashaholic No.131372]

>>131368
Its almost as if people in this thread are discounting lumens as a proper measurement of light output, they most certainly are. However you do need to be weary of certain manufacturers overstating their lumen outputs.
Heres my EDC, Jetbeam PC-10 550 OTF lumens for 30 minutes on one cell, 1 lumen for 120 hours on one cell.

[Anonymous No.131377]

>>131358
Slap one of the 100watt LEDs in there and up the battery,

>100W White High Power LED
>$109.99
http://www.ledssuperbright.com/30w-led-c-18/100w-white-high-power-led-p-226

You'll need the heatsink for it too,

>100W LED Heat Sink
>$47.50
http://www.ledssuperbright.com/30w-led-c-18/100w-led-heat-sink-p-244

Some guy put one or two of those on his bicycle. It was ungodly bright. It's the same guy that's crazy about Tesla coils and goes crazy stuff with them. I thin he's Australian, not sure though.

[Anonymous No.131383]

>>131377

That is not a single-core LED. Furthermore it has way too much surface area to collimate effectively into a long-range beam.

[Pinzfag, /k/'s resident flashaholic No.131384]

>>131377
You also need current regulators.
You could also just put in a preorder for the 4 sevens XM-18 which throws out 16,000 lumens but will set you back 2,400$

[Anonymous No.131385]

>>131384

Fuck 4sevens. If I wanted Fenix-made shit I would just buy a Fenix.

[Pinzfag, /k/'s resident flashaholic No.131388]

I have had a few fenix lights and they were plenty robust, in fact the barrel thickness was greater on my TA-30 than any other light I own. Some other options for a insanely bright searchlight would be polarion, but most of their shit is HID and useless unless you can carry around a billion batteries.

[Anonymous No.131389]

>>131383
One of the light companies just developed a single core 100w LED. not sure what lumens it is.

Here's the bike guy,

http://tesladownunder.com/WorldsBrightestBike.htm

He's using a shit load of LEDs it seems,

Specifications

Front lights:
15 x 100 W LEDs (12 white, 1 red, 1 blue 1 green: all approx 6000 lumens)
1500 W total
90,000 lumens
Beam 5 degrees
Rear lights:
3 x 100W LEDs (1 red, 1 blue 1 green)
300 W total
18,000 lumens
Beam 20 degrees
Total:
18 x 100 W LEDs (12 white, 2 red, 2 blue 2 green)
1800 W total
108,000 lumens (range 82,000 - 115,000)
ie approx 100,000 lumens total
Power:
3 x 12 V deep cycle 33 AH batteries
Run time:
est. 10 mins at 60 A 33 V

[Pinzfag, /k/'s resident flashaholic No.131391]

>>131389
Why you need something 20 times brighter than a car's headlamp on a bicycle I will never understand.

[Anonymous No.131398]

>>131391
BECAUSE SCIENCE!!!!

The guy is nutters for cool shit.

[Anonymous No.131401]

>>131391
becuz
>fuck the police!

[Pinzfag, /k/'s resident flashaholic No.131406]

>>131398
Its neat but I prefer practicality above all else.
What gets me most excited about led tech is the fact that a ton of urban centers are converting their streetlamps to LED Including most 711 chain stores and whatnot. Seeing that really makes me happy.

[Anonymous No.131411]

>>131388

Fenix does have the advantage of being cheaper than 4sevens stuff, and the same quality since they OEM their products anyway.

I've got a TK20 that has been through everything short of a nuclear holocaust, and it'd probably survive that too.

Left: TK11
Right: TK20

Just look at that fucking wall thickness. And that's at the threads where it's thinnest.

[Anonymous No.131413]

>>131406

They tried LED street lamps but their efficiency actually causes them to not work in the winter.

And by not work I mean they can't melt snow and get covered by it.

[Pinzfag, /k/'s resident flashaholic No.131415]

>>131413
We don't have that problem in commiefornia, Why don't they just make a small roof over each street light, like a 2x2 foot piece of bent sheet metal to keep the snow from encapsulating the lamp itself. Adding a heating coil would completely defeat the purpose of energy savings.

[Pinzfag, /k/'s resident flashaholic No.131420]

>>131413
In fact I would say almost 20% of the street lights in the bay area are now converted to LED.

[Anonymous No.131422]

[Anonymous No.131423]

>>131415
>Why don't they just make a small roof over each street light

Because snow doesn't behave like rain. When driven by wind it'll blow right up under shit and cover everything anyway.

[Anonymous No.131426]

>>131391
>Why you need something 20 times brighter than a car's headlamp on a bicycle I will never understand.
Just an observation based on what I've seen/experienced here in the UK.
No matter how many dayglo jackets, reflective strips, flashing LED lights etc you have, bicycles must have a magic 'cloaking field' around them, motorists fail to see them, leading to all sorts of 'hilarious' bike-in-the-ditch-and-minor-breaks-sprains-and-other-injuries scenarios etc.

I'd like to see a car driver explain to the Police how they failed to see something akin to a slow moving supernova and hit it.
Interested here, as I'm about to take up cycling again after a longish break (cf bike-in-the-ditch remark above), and will be making sure that the lights will be as bright as I can legally make them this time.

[Pinzfag, /k/'s resident flashaholic No.131430]

>>131426
Just cover your bike in RGB led tape and have it flash orange all the time. I'm pretty sure some cops would start harrasing you if you were using a light like that in traffic on a bike blinding every fucking person in front of you, In fact i might actually swerve into you for being such a inconsiderate cunt.
"But your honor, I couldn't see a damn thing! that kids light was blinding me!"

[Pinzfag, /k/'s resident flashaholic No.131431]

>>131430
Oops forgot image.

[Anonymous No.131432]

>>131430
fuck you dickweed. I cycle on an unlit road nearly every night. Not one driver will turn off their high beams till I shin my own light at them.

[Pinzfag, /k/'s resident flashaholic No.131434]

>>131432
Yeah, I am not a inconsiderate driver, I rarely use my brights anyways. But if some arrogant bicyclist started fucking with me with his intensely powerful light how is that different than me not turning off my brights. I think a light that bright on a bike is fucking dangerous to other people on the road.

[Anonymous No.131436]

>>131434
how about a light like that with variable brightness.

[Pinzfag, /k/'s resident flashaholic No.131439]

>>131436
Fair enough. I would love the ability to blind the shit out of drivers when they blind the shit out of me.
Buddie of mine has a hugely kitted out 4 runner with tons of offroad lights all over it, whenever someone flashes him with their brights, he has a FUCK YOU momentary button right on the steering wheel which blasts all the lights at full brightness for a moment. Quite handy.

[Anonymous No.131501]

>>131423
What I don't get is why snow it obscuring lamps. Are the lamps on the ground, are the lamps open at the top with a bowl to catch the snow, or is the snow blowing up and packing on the bottom of the lamps?

[Pinzfag, /k/'s resident flashaholic No.131506]

>>131501
Blowing and packing on the bottom of the lamps apparently. I think we should use heater coil impregnated glass (like the rear window of your car with the defroster on) I'm pretty sure those little heating elements only use 20 watts or so. Thus keeping it within the range of still saving a shitload of energy with the conversion.

[Anonymous No.131508]

>>131434
A light that bright only lasts 10 minutes with 3 deep cycle batteries hooked to it. I highly doubt anyone would be cycling with it. It'd be far better to only use 1 of the 100w LEDs. It's a little more than a motor cycle headlight in that respect and would be no more uncommon than a motor cycle.

>>131506
It still doesn't make sense unless the lamps are on the ground or on something low at least. We are talking about street lamps right?

[Pinzfag, /k/'s resident flashaholic No.131516]

>>131508
Snow is very sticky, If wind carries it up and it sticks to the glass on the bottom of the street lamp and another snow flake comes along and sticks to that one, its a vicious cycle. I have no doubt that it is a real problem that they have to find a way around. If you do it expect to make a lot of money because almost everyone is converting to led's for illumination EVERYWHERE! Makes me wish I invested in a LED company of some kind, making fixtures and what not. I could have been rich.

[Anonymous No.131551]

since everyone is talking about bikes and lights ill here instead of /n/; does anyone know of a helmet mounted light that can also has a "normal" flashlight form? Id really like to find a light I can use as a bike like and as a normal flashlight and if it was helmet mounted or I could just clip it to a helmet or something all the better

[Anonymous No.131557]

>>131508
>We are talking about street lamps right?

Yes we are. Snow is a bastard. It crusts over everything.

The idea that it must simply fall to the ground is sadly mistaken.

Pic related. Note how the snow clings to flat, vertical surfaces. The baffles needed on street lights make it even worse.

[Pinzfag, /k/'s resident flashaholic No.131562]

>>131557
Oh you mean stop lights, street lights are just for illumination however I can see both examples being a problem Why don't they just stick some low wattage heating pad type things around the collar?
>>131551
Zebralight.

[Anonymous No.131568]

>>131551
>/n/

Why bikes and lights on News?

[Anonymous No.131572]

>>131557
Solution is simple. Battery, solar charger, and heater.

Also, my area has all LED street lights now. We get 2 feet of snow at least once a year and it does not affect the LED street lights/LED traffic signal lights.

[Anonymous No.131577]

>>131568
/n/ is transportation as of a few years ago or something bro

[Anonymous No.131581]

>>131562
>Zebralight.

frankroo!

[Anonymous No.131582]

>>131572
>solar-powered heating during the winter

Not going to work. You do realize why winter even happens, right?

The solution everyone uses now is to have a heating coil in the glass that gets turned on whenever the light is being obstructed by snow. It runs off grid power the same way the lights themselves do.

It's still pretty energy efficient, since you're only running the heater when it's actually snowing.

[Pinzfag, /k/'s resident flashaholic No.131589]

>>131581
Also you can get a clamp for your bike that will utilize pretty much any flashlight out there, If a bare core floodlight with only 200 lumens isn't your thing The v60c is a fantastic upper mid-range light for a good price.

[Anonymous No.131593]

>>131562

Man... I have a ton of salvaged laptop cells I could use to run one of those for weeks but the only size light they make in that style is AA and uses an old LED.

Also LED lights used in snowy cities have heating elements embedded in the glass.

[Pinzfag, /k/'s resident flashaholic No.131601]

>>131593
Yeah they went to a reflector design which kinda sucks, The old H60 used a 18650 cell. I wish they would go back to the old bare core flood style with the minimalistic design. Bare core or a A-spheric lens is what you want for a headlamp, very very wide beam and no hotspot. Man, if someone made a torch in that form factor with a XM-L or even a SST-50 (drooool) powered by one 18650 I would pay an arm and a leg for it.

[Anonymous No.131600]

>>131589
>http://www.sunwayman.com/html/products/201108/59.html
>warns you not to use the charging system if running off 16340 cells.
>does not warn you not to use the charging system if running off CR123A cells.

[Anonymous No.131607]

>>131601

I'm pretty sure there's some cheap chinese knockoff with an xm-l that uses an 18650 but I'm not sure I'm comfortable strapping a 12W li-ion powered device of dubious build quality to my head.

[Pinzfag, /k/'s resident flashaholic No.131609]

>>131600
yeah..... that's why I didn't buy that light. All the reviews on CPF forums said if you use matched cells its no problem, that didn't really bother me as much as there's no tail-cap button you turn the light on with the ring. Taking the cells out and putting it in my intellicharge is the unbiggest deal.
As soon as the RRT-3 drops below 200 I'm going to buy it: >>131358
I was also looking at the o-light SR-51 for a 700 lumens for two hours class light but the big turn off for me was only two 18650 cells instead of 3 because of the stupid battery carrier.

[Anonymous No.131610]

>>131589
yeah I really cant leave the light on the bike when I lock it up so a light needs to go on and off the bike all the time for commuting. Thats why I was thinking headlamp but every other one ive seen is those little boxy things.

[Pinzfag, /k/'s resident flashaholic No.131615]

>>131607
Dude, all these lights are made in china, even surefire gets its drivers and led's from china, I'm pretty sure their "SUREFIRE BRAND" cells are from china as well.
Its the really cheap brands like the lights featured in the OP that scare me. Just get quality protected cells from a legit distributor and a good charger and you will never have issues.

[Pinzfag, /k/'s resident flashaholic No.131618]

>>131610
So make a mount that you can quickly detach, The headlamp world is extremely lacking.

[Anonymous No.131620]

>>131600
>use CR123 primaries
>plug into charger

>>131610

Lots of bike mounts are clipped or friction fit so you can just pull the light out and take it with you.

>>131615

The problem is not that it's made in china. The problem is that it is a shoddy knockoff made with no quality control.

Also Surefire's batteries are manufactured by Panasonic in the US.

Actually ALL CR123 primaries made in the US are manufactured by Panasonic because they run the only plant in the whole country.

[Pinzfag, /k/'s resident flashaholic No.131631]

>>131620
Which light are you implying is a dirty imposter from china, Not the zebra lights right? but some other light you saw like it with a XM-L?

[Anonymous No.131633]

>>131618
Yeah I was thinking of just getting a light with a belt clip and then attaching the belt clip onto some kind of sewed velcro piece that then has another piece of velcro on the helmet. That way I could clip the light on and of the helmet but also stick or unstick the velcro to reposition the light for task lighting if I need to work on the bike in the dark or just point it ahead when riding. And yeah most headlamps look pretty shit.

I saw something similar on someones helmet in some pics from afghanistan on /k/ but I dont think I saved it D:

[Pinzfag, /k/'s resident flashaholic No.131635]

>>131620
Oh and the v60c doesn't even come with that charger so if you want it you have to be competent enough to buy it which I guess is an agreement that you wont be retarded and plug it in with the wrong shit. The only other way to make it "consumer safe" out of the box would be to make it a non removable or proprietary battery and we don't want that do we?

[Anonymous No.131642]

>>131631
>Not the zebra lights right? but some other light you saw like it with a XM-L?

What? Yes. I thought that was clear.

>>131635

Or you could make the charger smart and not even initiate charge if the voltage and resistance characteristics of the battery don't match acceptable rechargeables.

Actually with smart electronics the charger could probably also handle the 16430s by detecting them and applying a different charging regimen.

[Pinzfag, /k/'s resident flashaholic No.131644]

>>131633
Surefires headlamp is bitchin I just wish they used a better led.

[Pinzfag, /k/'s resident flashaholic No.131645]

>>131642
Would be neat, but would also make it a 175$ light. Whereas you can get one now for 60 bucks on ebay and just charge the cells like a normal person would. Again, that's why I didn't buy the light and am waiting for the RRT-3 to come down in price. I also want to make use of that momenty switch port on the back with a wireless camera flash receiver for long exposure night photography

[Anonymous No.131649]

>>131645

Adding a proper control IC & support circuit to the design and flashing a program to it would only cost a couple dollars. Manufacturers are just cunts and always cut that corner.

Either that or they just cannot into smart charger engineering.

Come to think of it repeated design failures when they DO try suggests the latter.

[Pinzfag, /k/'s resident flashaholic No.131652]

>>131649
Lets start a flashlight company, you handle electronics, ill manage machining.

[Anonymous No.131658]

>>131430
>Just cover your bike in RGB led tape and have it flash orange all the time.

Umm, let's see en471 jacket, High Intensity Red LED rear lamp, 2x Front LED lamps (One 'dipped' to cover road @10 feet approx, other straight ahead. one flashing green led lamp on strap of my
daypack, dusk, not even full darkness, and I was still forced into a ditch to avoid being road pizza'd by a car. I thought I was very visible, obviously not, hence my interest in upgrading to higher wattage/Cd/lumen LCD lighting.

>I'm pretty sure some cops would start harrasing you if you were using a light like that in traffic on a bike blinding every fucking person in front of you,
Oh, for sure, a cyclist is an easier target for them than a motorist doing *exactly*the*same*thing*, or, heaven forbid, actually stopping arseholes in cars being such arseholes.

>In fact i might actually swerve into you for being such a inconsiderate cunt.

Tell you what, you give up your car for a couple of months, move somewhere where you cycle to and from work in the dark, have some prick in a 4x4 or 'SUV' (or whatever you lot care to call them this month) nearly kill you then we'll see if you still have that sort of attitude. You'll learn very quickly who the true 'inconsiderate cunts' of the road are.

>"But your honor, I couldn't see a damn thing! that kids light was blinding me!"

Naah, the 1W green laser's for doing that...

[Anonymous No.131659]

>>131652

Shit dog, I just want a charger that doesn't consider constant current to 4.2V to be an acceptable charging algorithm.

[Pinzfag, /k/'s resident flashaholic No.131668]

>>131659
We've been over this and over this, pay more for a better light with a proprietary non removable battery, abide by the rules of this charging system, or come up with a design yourself. I'm sure you could rework the charger base that it plugs into to charge the batteries more properly but honestly I have very little understand past common logic on how this shit works.
>>131658
I don't run bicyclists off the road, and as someone who is respectful to bicyclists on the road I would appreciate if they would respect me back by not fucking BLINDING ME. I just wanted to give you some more insight on how some people might react to a couple 100W leds being shined in their face by some invisible entity, for all someone may know you are just trying to fuck with them by shining a bright light in their face.

[Anonymous No.131676]

>>131668

<3 my i4.

Coworker got one off ebay that's apparently a fake and doesn't work properly off 110V mains.

[Pinzfag, /k/'s resident flashaholic No.131678]

>>131676
Beware, Chinese love to trick you into buying their shit. They are cheeky bastards.

[Anonymous No.131680]

>>131668
>>131676
>no LiFePO4 support

FUCK

[Pinzfag, /k/'s resident flashaholic No.131681]

>>131680
Might need to build your own for that one bub. You can get the chargers on a chip but it will be up to you to design the enclosure. Are there any lights that accpet LiFe batteries or are you building the light yourself. (might want to integrate the charger in that situation rather than making it a separate device)

[Anonymous No.131687]

>>131681

Pretty much anything that takes both 3V primary and 3.7V li-ion will also take 3.2V LiFePO4.

Also a lot of lights that take 3V but not 3.7V safely will still be okay with 3.2V. eg: Romisens.

Fortunately LiFePO4 is an extremely resilient chemistry that can take a lot of abuse so making charge circuits is easy even with cheap components.

[Pinzfag, /k/'s resident flashaholic No.131696]

>>131687
Do you have a good source for cells?

[Anonymous No.131702]

>>131696

Local hobby shop sells 1.1Ah to 1.4Ah 18650s for $7ish depending on brand. They do not sell online unfortunately.

The A123 Systems cells run close to $8 for 1.1Ah but are fantastic.

[Anonymous No.131704]

Lumens do not stack.

That means if those LEDs are 200 lumen LEDs, the most you're actually getting is 200 lumens.

Photon flux density is a different story.

pic related - I build and design lights. Don't get fooled by bullshit marketing.

[Anonymous No.131705]

>>131383


>doesn't know about focusing and combining optics.

[Pinzfag, /k/'s resident flashaholic No.131706]

>>131702
They don't offer a 123 size cell :(
Once I run out of primaries i need to buy some rechargable "RCR123a" cells for my PC-10 to get the full 550 lumen output. Still on the fence about which cells to get. However I'm definitely leaning towards AW.

[Pinzfag, /k/'s resident flashaholic No.131708]

>>131704
Can you explain just exactly why it doesn't stack?

[Anonymous No.131710]

>>131705

Collimation is a function of surface intensity. No matter how big an optic you use, a smaller and more intense light source will perform better in an optic of the same size.

>>131704
>>131708

It does stack. What is this horse shit?
The lumen is essentially a measure of how many photons the light source(s) are shitting out. If you combine two 200lm sources, your total emittance is 400lm.

[Pinzfag, /k/'s resident flashaholic No.131711]

>>131704
So if lumens don't stack, Then why are there so many led cores on that "led"

[Anonymous No.131712]

>>131706

Keep in mind that LiFePO4 are lower voltage and lower capacity than LiCo2 (3.7V) so it's not the best choice for run time or performance (if your performance is voltage-limited).

LiFePO4 is used for its ridiculous discharge tolerance and refusal to explode under adverse conditions.

[Pinzfag, /k/'s resident flashaholic No.131713]

>>131712
Yeah I require 3.6 volts at least to get the full lumen output of my light so those wont do it.

[Anonymous No.131717]

>>131710
>a measure of how many photons the light source(s) are shitting out

I should clarify this statement by noting that the measure is weighted for human vision. ie: green photons are worth more on the scale than red ones due to human eye photosensitivity

Regardless, the lumen is light output and is additive. Doesn't matter how effective it happens to be at a task; there are other measures for that.

[Anonymous No.131739]

>>131711

That's a horticultural array. Apparently you don't knwo much.

Lumens do not stack. The beam will only be as apparently bright as the brightest and closest source.

Fuck, even basic photobiologists know this.

[Anonymous No.131740]

>mfw people think lumens 'add' when the human eye works on a logarithmic scale

[Pinzfag, /k/'s resident flashaholic No.131745]

>>131739
How do you define "brightness" then, You say it is only as bright as the closest brightest source I'm having trouble understanding how you are contextualizing all this.
I am aware that there are different color led cores on that panel for the explicit reason of growing plants. However there are only 3 and very many duplicates of those 3 core types on this panel.

[Anonymous No.131747]

>>131745

Learn about the only unit that matters in light - photon flux density.

Lumens is outdated and shit, and only applies to humans.

[Anonymous No.131748]

>>131745
>only 3 core types.

Wrong. 7. 4 visible range, 3 non-visible.

Photon output matters.

[Pinzfag, /k/'s resident flashaholic No.131749]

Yeah I kinda just realized that what we are debating is whether or not they double with intensity when you have two cores, Obviously it gets brighter its just not exactly double.

[Anonymous No.131750]

>>131749

It's nowhere close to double by apparent brightness.

[Anonymous No.131829]

>>131749
>>131750

That's completely irrelevant for the measure, though. Lumens add together linearly. The eye's logarithmic perception of brightness is of no consequence to the metric.

100 + 100 = 200 lumens doesn't necessarily appear twice as bright, but the number of lumens has still doubled.

[Anonymous No.131837]

>>131739
>>131747
>>131750

Quit backpedaling. First you argued that 1000lm + 1000lm literally does not equal 2000lm, which is completely fucking wrong. Now that you've been called out you're trying to pass it off as perceived brightness, which has no bearing on whether lumens sum.

[Anonymous No.131840]

What is the best color light for max visibility? I mean what color for you to see what you are shining the light on.

[Anonymous No.131846]

>>131840
Green. Don't know the specific wavelength but google does.

[Anonymous No.131847]

>>131840
>>131846

Yes, green is where sight peaks. Using only one color is going to provide very poor contrast though.

[Anonymous No.131849]

>>131837
If I might interject, fuck that guy and his "apparent brightness" bullshit, because that's exactly what lumens represent, as opposed to just flux.

And so yeah, 1 lumen + 1 lumen = 2 lumens, provided the source projects into the same space.

[Anonymous No.131854]

>>131849
>as opposed to just flux.

wut

http://en.wikipedia.org/wiki/Lumen_%28unit%29

[Anonymous No.131858]

>>131854
Flux, generically, is power through either an area or a solid angle. Light is usually measured this way for physical purposes.

Lumens is special, because it's a flux measurement, but takes into account how the eye perceives light. It's purpose is in the application.